Within this work, the thermal stress build-up of chemically vapor deposited TiCN/α-Al₂O₃ bilayer coatings was controlled by tuning the coefficient of thermal expansion (CTE) of the substrate material. This was implemented through a Co content variation from 6 to 15 wt.% in WC-Co substrates, which exhibit higher CTEs with increasing Co contents and thereby approach the CTE values of TiCN and α-Al₂O₃. High temperature X-ray diffraction was employed to determine thermal expansion of an α-Al₂O₃ powder. Crystallographic texture of the α-Al₂O₃ coating layer was evaluated by electron backscatter diffraction and taken into consideration in order to assign the appropriate in-plane CTE. This consideration indicated a lower CTE mismatch of α-Al₂O₃ with WC-Co, compared to TiCN with WC-Co. X-ray diffraction was further utilized for the determination of residual stress in TiCN and α-Al₂O₃, demonstrating a decrease in both layers for Co contents below 12.5 wt.%. Decreasing stress signaled the formation of thermal crack networks confirmed by scanning electron microscopy surface images. Lower residual stresses were determined in TiCN compared to α-Al₂O₃ layers of bilayer coatings, contradicting finite element simulations of thermo-elastic stress, that were carried out to illustrate the stress relaxation effects caused by thermal cracks. Monolayer TiCN coatings were annealed at 1000 °C, to replicate stress relaxation taking place during α-Al₂O₃ deposition, exhibiting a similar residual stress state to TiCN base layers of bilayer coatings. Thermal crack formation was found to be the dominating stress relaxation mechanism in α-Al₂O₃, while TiCN undergoes further relaxation through secondary mechanisms.

内这项工作中，热应力积聚的化学气相淀积的的TiCN /α-Al系₂ ö ₃双层涂层是通过调节基底材料的热膨胀（CTE）的系数进行控制。这是通过一个Co含量变化实现从6至15％（重量）在WC-Co的底物，其随着增加Co的含量表现出更高的热膨胀系数，并由此接近的TiCN的CTE值和的α-Al ₂ ö ₃。高温X射线衍射采用以确定的α-Al的热膨胀₂ ö ₃粉末。所述的晶体学织构的α-Al ₂ ö ₃通过电子反向散射衍射评估涂层并考虑到涂层，以分配适当的面内CTE。这种考虑表示的下CTE失配的α-Al ₂ ö ₃用的WC-Co，相比的TiCN与WC-Co的。X射线衍射进一步用于残余应力的TiCN和α-Al系的判断₂ Ó ₃，展示了低于12.5％（重量）在两个层为Co的含量的降低。应力的减小表明通过扫描电子显微镜表面图像已证实形成了热裂纹网络。下残余应力在确定的TiCN相比的α-Al ₂ ö ₃与热弹性应力的有限元模拟相矛盾的双层涂层的层，其目的是说明由热裂纹引起的应力松弛效应。单层的TiCN涂层在1000退火℃下，向复制应力松弛正在发生期间的α-Al ₂ ö ₃沉积，表现出类似的残余应力状态到双层涂层的TiCN基层。热裂纹形成被认为是在α-Al系的主导应力衰减机构₂ ö ₃，而通过的TiCN继发性机制经历进一步的弛豫。